Personality: According to Aizen, all forms of rationality, memory retention, speech, and intelligence were purposely removed to enhance his power.[4] Because of this, Wonderweiss' personality is very childlike, comparable to someone with low functioning autism. For example, when sent on a mission to kill, he instead played around with a dragonfly. He shows some hostility, firing a defensive Bala blast at one point, but quickly reverts to his usual childlike state after doing so. In a later confrontation, Wonderweiss displays a higher level of hostility by stabbing Captain Jūshirō Ukitake through the chest without any warning or provocation.

Wonderweiss does not speak in sentences due to his modifications, only saying a few drawling syllables at a time such as an infant would. The only coherent phrase he has ever spoken is his own name, immediately after being "reborn" as an Arrancar. Kaname Tōsen remarks that Wonderweiss, like himself, is a pure being (though he remarks he doesn't quite know what exactly is pure about him) who often tend to stick together. He claims this is why Wonderweiss follows him everywhere. It is implied that he tried to restrain Gin Ichimaru from approaching Tōsen because Wonderweiss was wary of him.Likes: Dragonflies, toys, and spending his time playing; when not needed for something else. Wonderweiss has very little set about his personality, and that means his being is constantly fluctuating; meaning he rarely likes or dislikes the same things from minute to minute; outside of the absolute basics.Dislikes: Wonderweiss has very little set about his personality, and that means his being is constantly fluctuating; meaning he rarely likes or dislikes the same things from minute to minute; outside of the absolute basics.

History:

Bleach series canon:

Wonderweiss was first seen at his transformation into an Arrancar by Sōsuke Aizen. His original form is seen wrapped in what appears to be bandages while a barrier surrounds his body. Numerous Espada were present at his "birth", including Coyote Starrk, Tier Harribel, Ulquiorra Cifer, Nnoitra Gilga, Luppi Antenor (still instated as an Espada at the time), Grimmjow Jaegerjaquez, Aaroniero Arruruerie, and Yammy Llargo.

Wonderweiss was among the Arrancar present during the third invasion of Karakura Town. He is yelled at by a bored Yammy for playing with a dragonfly instead of paying attention to the battle. This was until Kisuke Urahara intervened in Luppi's fight, as Wonderweiss tries to grab Urahara's hat from behind. Urahara senses his presence and counterattacks, but Wonderweiss dodges the attack and fires a Bala. Urahara dodges the attack and confronts Wonderweiss asking him what was the technique he just used as he had never seen it before. Urahara is then attacked from behind by Yammy, who explains that it was a Bala blast as he fires a multitude at the fallen body of Urahara. Wonderweiss once again loses interest and just sits there. He is shortly pulled back to Hueco Mundo via Negación once Ulquiorra Cifer completes his mission.

Wonderweiss arrives in the Fake Karakura Town through an extremely large Garganta, interrupting the battle between the Primera Espada Coyote Starrk and Captains Shunsui Kyōraku and Jūshirō Ukitake, which surprises Starrk. Wonderweiss is accompanied by Hooleer, which Captain Sajin Komamura recognizes as the same creature seen looming over the numerous Gillian who created the Negación that transported Aizen, Gin, and Kaname from Soul Society to Hueco Mundo when they were revealed as traitors.

Immediately after arriving, Wonderweiss suddenly appears behind Jūshirō and impales him with his own hand, injuring the captain and causing him to fall towards the buildings below. Shunsui attempts to attack Wonderweiss, but is hit in the back by an opportunistic Cero from Starrk sending him towards the ground with Jūshirō. Starrk comments that the arrival of Wonderweiss means that Aizen has grown tired of the battle. Wonderweiss then lets out a battlecry which causes a shockwave to break Captain Tōshirō Hitsugaya's ice obelisk, freeing Harribel. The cry also seems to "blow" away the smoke left after Captain Suì-Fēng's Bankai attack on Baraggan Louisenbairn, revealing that the attack had no effect on him. Wonderweiss continued to scream and Hooleer vomited many Gillian-class Menos from its mouth. When the Visored Mashiro Kuna attacks his companion killing the creature, Wonderweiss simply stares at her. Shocked at seeing his companion die, Wonderweiss then charges his Cero from his mouth, but before he can fire it, Mashiro kicks him in the face. He is later seen lying on the ground with Mashiro shouting "Yay! Victory!"

Wonderweiss proves not easily defeated and attempts to attack Mashiro from the ground, but his attack is blocked and he is kicked away. He launches himself directly at her, but she grabs him by the face and slams his head into the ground. Wonderweiss gets up and lets out a battlecry as he grabs Mashiro by her scarf and uses it to throw her blocks away crashing into various buildings. They both launch at each other with Mashiro firing off her Mashiro Super Cero, which Wonderweiss successfully counters with his battlecry. Mashiro immediately attacks him, punching him until suddenly her mask shatters. Taking advantage of her confusion, Wonderweiss punches her in the face, injuring her severely and rendering her unconscious. Before he can hit her again, his fist is blocked by Kensei Muguruma, who states that he is not mature enough to show restraint when it comes to kids. Kensei throws Wonderweiss, sending him flying into the buildings below.

Wonderweiss was knocked unconscious by the impact with the building and was found after the end of the fight. While an enemy combatant, some level of pity was taken upon him by Orihime Inoue, who healed his physical wounds; and discovered the modifications placed on him. She was able to undo some of them, allowing Wonderweiss to regain some semblance of functionality, as well as releasing him from the strongest of Aizen's commands. While still heavily damaged mentally from Aizen's work; he no longer holds the high levels of hostility toward the world in general, and no longer has a overwhelming drive to destroy and kill everything he sees that is evolutionary higher than a dragonfly. Because of this, he was released back to Hueco Mundo under Tier Harribel's care. After an undetermined amount of time, he vanished from Hueco Mundo once more, and has recently been reported wondering around various parts of the various worlds; although no reports of damage or hostility on his part have been discovered.